However, you don’t actually need to do that with CSS, you can just add some additional CSS to override the theme’s.

input[type=”text”] {
color: #000000!important;
}

Add that in Dashboard -> Appearance -> Customize -> Additional CSS and it will override all other styles for the input type ‘text’ colour (because its using !important). Or you be more specific with your CSS selectors (high specificity ‘wins’) like:

#ee-single-page-checkout-dv input[type=”text”] {
color: #000000;
}

Applies specifically to the single page checkout form fields and should override the woocommerce styles.